The House speakership is traditionally a capstone to one's career, but newly inducted House Speaker Paul Ryan is the youngest person to serve in the role in nearly 150 years. With the Republican Party suffering from substantial internal strife, Ryan emerged as the only consensus candidate who could garner sufficient votes to wield the speaker's gavel at this time. However, much like Pope Benedict XVI in the long succession of the papacy, Ryan is more destined to serve as the transition between two eras rather than to create an extensive one of his own.

Reluctant to take on the speakership in the first place, Ryan will most likely focus on accomplishing discrete, key milestones rather than becoming an institution in his own right.

Most notably, Ryan has set his sights on leading efforts to achieve comprehensive tax reform, which is an elusive, once-in-a-generation goal. As chair of the House Ways and Means Committee, he had already begun laying the foundation for an ambitious rewrite of the tax code during the next presidential administration. While Ryan will no longer be able to get as deep into the weeds on tax reform, he will be in a far better position to shepherd the overall legislative process to fruition.

Getty Images

Rep. Paul Ryan (R-WI) leaves after a House Republican Conference meeting October 20, 2015 at the Capitol in Washington, DC.

Ryan will nevertheless need to temper his ambitions for his other top priority, entitlement reform, which would seek to contain the mandatory spending that comprises most of the federal budget and for which a vast partisan divide has long obstructed significant changes. He is likely to seek moderate changes to entitlement programs as bargaining chips, rather than pursuing a grand bargain on a complete overhaul, an objective that Ryan's predecessor, John Boehner, repeatedly failed to obtain despite his repeated attempts. Before Ryan assumed the speakership, limited changes to Medicare were used to reach a larger deal on government spending, and future incremental fixes are far more likely than Ryan's sweeping proposal to privatize Medicare.

Although Ryan fashions himself a principled conservative, he has shown himself in recent years to also be a pragmatic dealmaker. For example, he was co-architect of a two-year budget deal that he negotiated with Democratic Senator Patty Murray. Ryan also knows not to bite off more than he can chew. On his round of the Sunday morning shows last weekend, he made clear that he had no intention of pursuing immigration reform while President Obama remains in office. Though, he is unlikely to tackle the issue, even when there is a new occupant in the White House.

Whoever controls the Oval Office next will be a key variable in how long Ryan remains as speaker. If presumptive Democratic presidential nominee Hillary Clinton wins next year's election, which would also give the Democrats a good shot at re-gaining control of the Senate, then Ryan is unlikely to want to overstay his welcome in Washington by being relegated to the role of opposition leader. Instead, once he is able to negotiate comprehensive tax reform with Clinton and heir apparent Democratic Senate Leader Chuck Schumer, Ryan will most likely be ready to move on to greener pastures.

However, if a Republican wins the White House, then Ryan might be more inclined to stay longer in the nation's capital as the GOP's control of both the executive and legislative branches would afford him much greater influence over future federal policymaking.

Either way though, Ryan undoubtedly still harbors presidential ambitions, despite his repeated statements to the contrary. And it is not easy to convert from being speaker to commander-in-chief – in fact, only James Polk has been successful at doing so. That is why Ryan's path to the White House probably runs back through his home state of Wisconsin. Although current Governor Scott Walker is not subject to any term limit, he has demonstrated his own aspirations for higher office. Ryan very well could leave Washington to seek election as governor of Wisconsin, perhaps in 2022. After accomplishing tax reform as speaker and demonstrating his chief executive bona fides in Wisconsin, Ryan would be more than ready to make a run for the highest office in the land.

Commentary by Stephen A. Myrow, managing partner of Beacon Policy Advisors LLC, an independent policy research firm based in Washington, DC. He has served in various government roles, including as a senior Treasury Department official in 2008-2009.Follow him on Twitter @smyrow.